Sustainable recycling of waste crystalline silicon photovoltaic modules based on heavy liquid separation and metal chloride etching

Abstract

This study proposes an environmentally friendly treatment process based on heavy liquid separation and metal chloride etching for the recovery of valuable resources from crystalline silicon photovoltaic (c-Si PV) modules. It addresses key limitations of conventional recycling methods, such as low component separation efficiency and heavy reliance on strong acids and alkalis in hydrometallurgical steps. In the separation stage, the zinc bromide (ZnBr2) heavy liquid method is used to achieve highly efficient (>98%) separation among glass particles, solar cells, and solder strips. In the purification stage, a metal chloride etching approach is employed. Under hydrothermal conditions, a synergistic etchant composed of aluminum chloride hexahydrate (AlCl3·6H2O) and hydrogen peroxide (H2O2) completely removes silver (Ag), aluminum (Al), and silicon nitride (Si3N4) from the solar cell surface. Then copper chloride dihydrate (CuCl2·2H2O) solution is utilized to effectively remove lead (Pb) and tin (Sn) from the solder strips. Ultimately, valuable materials such as silicon wafers, silver chloride (AgCl), and copper (Cu) are successfully recovered. Life Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) confirm that the proposed process is a sustainable recycling solution for c-Si PV modules, offering both environmental benefits and industrial scalability. Building on these results, this study proposes a novel green and low-toxic recycling strategy for end-of-life c-Si PV modules, providing a viable technical pathway toward sustainable development of the photovoltaic industry.